黄土—泥岩型滑坡形成机制数值模拟研究

发布时间：2018-01-20 02:47

本文关键词： 天水市黄土－泥岩滑坡物理力学参数 FLAC3D数值仿真形成机理　出处：《长安大学》2014年硕士论文　论文类型：学位论文

【摘要】：位于甘肃东南的天水市属典型河谷城市，受地形地貌、地质构造、岩土性质、降雨等控制和影响，滑坡、崩塌、泥石流等地质灾害发育且活动频繁，严重威胁着人民生命财产安全。其中广泛发育于天水地区的黄土-泥岩型滑坡严重影响着当地的工程经济建设。因此，本文依托国家自然基金项目“考虑地表水沿裂缝浸入的黄土斜坡稳定性研究”，通过大量区域调查，选择了天水麦积区职业技术学院南侧斜坡处发育的一典型黄土－泥岩型滑坡为研究对象，运用现场测绘、挖探与取样、室内外试验、数值分析等，研究了该类型滑坡形成机理和运动过程，旨在为天水地区此类滑坡稳定性预测与防治以及国土规划提供理论依据。滑坡所在斜坡区地质结构是由第四系黄土层和白垩系泥岩组成，典型的“双层异质”坡体结构特征，斜坡坡度约25°。加之区域丰富的降雨量，常是此类滑坡产生的外在诱发因素。研究发现，该滑坡是一中型黄土－泥岩顺层滑坡，滑动面为黄土泥岩接触面，滑动面受岩层产状控制，滑面倾角约8。后缘黄土形成的张拉面陡直，呈现出典型蠕动－拉裂、滑移－解体和剪断－挤出的破坏模式。通过对滑坡区黄土室内三轴试验，得出不同含水率下c、的变化规律，粘聚力c和内摩擦角随着含水率的增大而减小。当含水率小于18%时粘聚力c减小幅度较大，当含水率大于18%时粘聚力c变化幅度较小。同时，分别研究了相同含水率（20%）与不同围压（50kPa、100kPa、150kPa、200kPa、250kPa、300kPa、350kPa、400kPa、450kPa和500kPa），以及相同围压（50kPa、100kPa、200kPa、400kPa）与不同含水量（10%、12%、14%、16%、18%、20%、22%和24%）条件下，黄土应力应变关系曲线，可以看出随着含水率的增大，应力应变曲线逐渐减小，当围压小于150kPa时曲线呈弱化型；当围压大于150kPa时呈硬化型的结论。通过四组现场原位渗水试验，得出滑体后缘原状马兰黄土渗透系数为2.26m/d，，经过人工碾压的滑体土渗透系数0.23m/d和破碎泥岩的渗透系数0.91m/d，表明地表水的入渗对整个滑坡的产生起到决定性的作用。现场实际测绘了滑坡滑动后的工程地质平面图（1:1000）和3条纵断面图（1:500），并利用原有滑坡区地形图（1:10000）运用surfer软件恢复了滑坡滑动之前斜坡三维断面图（1:500）。将滑动前后的三维纵断面通过CAD-Surfer-Flac3D数据文件转换技术，建立了滑坡数值仿真的三维计算模型。通过工程地质分析，提出了黄土-泥岩型滑坡变形演化机理表现为三阶段，即蠕动－拉裂、滑移－解体和剪断－挤出。基于Flac3D数值仿真计算分析了滑坡体的应力应变特征及滑坡形成机理，即滑坡前缘向两边滑移扩散的机理，并与工程地质分析进行对比，结果基本一致。最后分析了该类滑坡运动机理，即缓动和低速效应，表现为滑速低、滑距小等特点。
[Abstract]:Tianshui City, located in southeast Gansu Province, is a typical river valley city, which is controlled and affected by topography, geological structure, rock and soil properties, rainfall and other geological disasters, such as landslide, collapse, debris flow and other geological disasters. It is a serious threat to the safety of people's life and property. The loess-mudstone landslide, which is widely developed in Tianshui area, seriously affects the local engineering and economic construction. This paper relies on the National Natural Fund project "considering the stability of loess slope immersed by surface water along cracks", through a large number of regional investigations. A typical loess-mudstone landslide developed on the southern slope of Tianshui Maiji Vocational and Technical College was selected as the research object. The site mapping, digging and sampling, indoor and outdoor tests, numerical analysis, etc. The formation mechanism and movement process of this type of landslide are studied in order to provide theoretical basis for the stability prediction, prevention and control of this kind of landslide and land planning in Tianshui area. The geological structure of slope area is composed of quaternary loess layer and Cretaceous mudstone, typical "double layer heterogeneous" slope structure characteristics, slope gradient about 25 掳, coupled with abundant rainfall in the region. It is found that the landslide is a middle-sized loess-mudstone bedding landslide, the sliding surface is loess mudstone contact surface, and the sliding surface is controlled by the occurrence of rock strata. The slope angle of the slip surface is about 8. The tensile surface formed by the loess at the rear edge is steeply straight, showing a typical failure mode of creeping and pulling, sliding and disintegrating, and shearing and extruding. Through the laboratory triaxial test of loess in landslide area, the variation law of c, is obtained under different moisture content. The cohesion C and the internal friction angle decrease with the increase of moisture content. When the water content is less than 18, the cohesion C decreases greatly, and the cohesion c changes slightly when the water content is greater than 18. At the same time. The same moisture content and different confining pressures (50 KPA, 100 KPA, 150 KPA, 200 KPA, 250 KPA, 300 KPA, 350 KPA, respectively) were studied. 400kPa450kPa and 500kPaA, and the same confining pressure 50kPa100kPa200kPa200kPa400kPa) with different water content (10%). Under the conditions of 22% and 24%, the stress-strain curve of loess can be seen to decrease with the increase of water content. When the confining pressure is less than 150 KPA, the curve is weakened. When the confining pressure is greater than 150 KPA, the conclusion is that it is sclerosed. Through the in-situ seepage test of four groups, the permeability coefficient of undisturbed Ma Lan loess in the rear edge of sliding body is 2.26 m / d. The permeability coefficient of the landslide is 0.23 m / d and the permeability coefficient of broken mudstone is 0.91m / d, which indicates that the infiltration of surface water plays a decisive role in the whole landslide. The engineering geological plan (1: 1000) and the 3 longitudinal sections (1: 500) after landslide sliding are actually plotted on the spot. Using the original topographic map of landslide area (1: 10000) and using surfer software to restore the slope 3D section map before landslide slide (1: 500). The 3D profile before and after sliding is transformed by CAD-Surfer-Flac3D data file. A three-dimensional model for numerical simulation of landslide is established. Based on the analysis of engineering geology, the deformation and evolution mechanism of loess mudstone landslide is presented as three stages, that is, creeping and pulling fracture. Based on the Flac3D numerical simulation, the stress-strain characteristics of landslide and the mechanism of landslide formation are analyzed, that is, the mechanism of slip diffusion from the front edge to both sides of the landslide. Compared with engineering geological analysis, the results are basically consistent. Finally, the mechanism of landslide movement, that is, slow-moving and low-velocity effects, is analyzed, which is characterized by low sliding speed and small slip distance.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P642.22;TU444

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